The present invention refers to a method and apparatus for determining the position of an elongated, relatively narrow object relative to the surface of an obstructing, preferably disk-like body in front of said object and oriented at an angle thereto, and, more particularly, to such a method and apparatus which employs electromagnetic radiation, particularly ionizing radiation, for guidance of the movement of an associated treatment equipment, particularly for laser welding.
Previously, electromagnetic radiation has been used for finding hidden materials, such as narcotics, explosives and other contraband etc. One example is disclosed in GB-A-2 055 198. Other examples are disclosed in U.S. Pat. No. 5,600,700 and U.S. Pat. No. 5,648,619.
WO 95/00725 describes the manufacture of a so-called sandwich element, i.e., a double-walled sheet metal element, particularly for use in the manufacture of ships. However, it is not evident from WO 95/00725 how this manufacture including welding of the spacing walls of this element is to be carried out. Further, WO 95/00725 deals with plane sheet metal walls having standardized and, preferably, right-angular shapes, which makes the problem simple.
Another and more difficult problem occurs when sandwich elements are to be made, which have conical or double-curved surface, such as in rocket nozzles or the like. Then very high requirements as to precision are required when it comes to welding through the obstructing sheet wall against the narrow side or edge of the spacing means, the width of which is less than 1 mm.
Therefore, the main object of the present invention is to solve this problem and this is achieved by means of a method according to the invention, which is substantially distinguished in that from the side of the body remote from the object is directed, under approximate movement in the longitudinal direction of the object, at least one precisely collimated radiation beam obliquely to the object under simultaneous oscillating or scanning motion at right angles thereto; that the radiation back-scattered from the object is collected at the same side of the body and is brought to form therefrom a signal which is compared with memory stored signals for the desired correct position of the object relative to the body for guidance of the radiation beam motion along the object and hence also the motion of the associated equipment. For obtaining the highest possible precision in the method it is preferred, that also the back-scattered radiation is collimated.
In accordance with the invention, a device for carrying out this method comprises a detecting device for determination of the position of an elongated and relatively narrow object relative to the surface of an obstructing body in front of said object and oriented at an angle thereto and, preferably an object of disk-like shape, by means of electromagnetic and preferably ionizing radiation for guidance of the movement of an associated treatment equipment, particularly for laser welding. The features substantially distinguishing said device are substantially that, the detecting device which is arranged at the same side of the disk-like body as the sender device, is adapted to receive a radiation emitted from the sender device towards the object and back-scattered from the object and to form therefrom a signal and in that a comparator is arranged to compare said signal with predetermined preference signals stored in a memory for the desired correct position of the object relative to the body for guidance of the movement of the radiation beam along the object and hence also the motion of the associated equipment.
By the inventive method and device it is now made possible, in a surprisingly effective manner, a rapid and effective operation with high precision in the function., such as in laser welding of double-curved and double-walled panels. In doing so the welding speed will be allowed to be as great as 1000 mm per minute.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.